The GM Performance Parts rpm control protects expensive engines from damage caused by missed shifts and broken drivetrains. This "soft touch" rev limiter's advanced computer circuitry cuts the spark to one cylinder at a time, then fires the cylinder on the next cycle. This smooth rev-limiting feature eliminates backfires and engine damage. The limiter is calibrated for four, six, and eight-cylinder engines with a plug-in module. The maximum engine speed is also set with plug-in "chips;" three modules (6000, 7000, and 8000 rpm) are included. Additional modules are listed below. Technical Notes: The chips for 6 and 8 cylinders are included in this kit. No chip is required when using it with a 4-cylinder application.